Field of Technology
The present disclosure relates to an organic light emitting display device, a method of manufacturing the same, and a head-mounted display (HMD) including the same.
Discussion of the Related Art
With the advancement of information-oriented society, various requirements for display devices for displaying an image are increasing. Therefore, various display devices such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light emitting display devices, etc. are recently being used.
As a type of display device, organic light emitting display devices are self-emitting display devices and are better in viewing angle and contrast ratio than LCD devices. Also, since the organic light emitting display devices do not need a separate backlight, it is possible to lighten and thin the organic light emitting display devices, and the organic light emitting display devices are excellent in power consumption. Furthermore, the organic light emitting display devices are driven with a low direct current (DC) voltage, have a fast response time, and are low in manufacturing cost.
The organic light emitting display devices each include anode electrodes, a bank that divides the anode electrodes, a hole transporting layer, an organic light emitting layer, and an electron transporting layer that are formed on the anode electrodes, and a cathode electrode formed on the electron transporting layer. In this case, when a high-level voltage is applied to the anode electrode and a low-level voltage is applied to the cathode electrode, a hole and an electron respectively move to the organic light emitting layer through the hole transporting layer and the electron transporting layer and are combined with each other in the organic light emitting layer to emit light.
In the organic light emitting display devices, an area where an anode electrode, an organic light emitting layer, and a cathode electrode are sequentially stacked is an emissive area that emits light, and an area where a bank is provided is a non-emissive area that does not emit light. The bank defines the emissive area.
The anode electrode is connected to a source or drain electrode of a thin-film transistor (TFT) through a contact hole and is supplied with a high-level voltage. Due to a step height of the contact hole, it is difficult for the organic light emitting layer to be uniformly deposited in the contact hole, and thus, the organic light emitting layer is not formed in the contact hole. That is, the contact hole is covered by the bank.
Recently, since small organic light emitting display devices applied to mobile devices and the like have a high resolution, a pixel size is progressively reduced. However, the contact hole is formed through a photo process, and due to a limitation of the photo process, the contact hole cannot be formed to less than a certain size. That is, despite the pixel size being reduced, there is a limitation in reducing the contact hole.
The contact hole is disposed in the non-emissive area, and thus, if the pixel size is reduced, an area ratio of the non-emissive area becomes higher, and an area ratio of the emissive area becomes lower. If the area ratio of the emissive area becomes lower, the emission luminance of the emissive area should increase, and for this reason, a lifetime of the organic light emitting layer is reduced.
Recently, head-mounted displays each including an organic light emitting display device are being developed. The head-mounted displays are glasses-type monitor devices for virtual reality (VR), which are worn in a glasses type or a helmet type and form a focal point at a distance close to eyes of a user. However, in the head-mounted displays, an image displayed by the organic light emitting display device is seen in just front of eyes of a user, and for this reason, if a ratio of an area occupied by a non-emissive area in each pixel is high, the non-emissive area is seen in a lattice pattern as illustrated in FIG. 1.